The present invention relates to a foam body made integrally of at least a layer of foam material having a great resilience and at least a layer of foam material having a great capability to absorb shock. These two layers of foam materials are identical in terms of the kinds of ingredients they contain but are different in terms of the proportions by which the ingredients are prepared.
Depending on the purpose of a foam body, a plastic foam material can be used to make a soft foam body or a rigid foam body by adjusting the proportions by which the ingredients are contained in the plastic foam material. Similarly, a plastic foam material can be used to make a foam body having great resilience or a foam body having great capability to absorb shock. It is well known that a foam body having great resilience is also provided with a shock-absorbing capability to a certain extent, and vice versa. For this reason, it is necessary that the term "great resilience" is defined in a precise manner here. If an iron ball having a weight of 33.5 g is allowed to make a free fall from a height of one meter on a foam body having a thickness of 10 centimeters, the foam body capable of making the iron ball to make the first bounce of 10 centimeters or more is said to have a great resilience while the foam body capable of making the iron ball to make the first bounce of less than 10 centimeters is said to have a great shock-absorbing capability. The quantity of resilience of the foam body is directly proportional to the quantity of the first bounce of the iron ball that falls freely on the foam body. On the other hand, the quality of the shock-absorbing capability of the foam body is inversely proportional to the quantity of the first bounce of the iron ball that falls freely on the foam body.
In order to make good use of foam bodies having various resilient and shock-absorbing characterstics, it is a common practice that various kinds of foam bodies are combined in a variety of forms. For example, a shoe insole or a shoe insert is generally made of foam bodies having respectively great resilience and great shock-absorbing capability so as to ensure the wearing comfort. In other words, the shoe insole or the shoe insert is generally a laminated body comprising layers of various foam materials. The manufacture of the shoe insert is a case in point. Such shoe insert is composed of layers of foam bodies, which are adhered together by a bonding agent, and is defective in that the labor cost of making the shoe insert is high, and that the bonding agent used to glue the layers of foam bodies is a potential source of environmental pollution, and further that the quality of the shoe insert is undermined by the topical formation of gas bubbles in the shoe insert caused by the bonding agent which evaporates in the course of baking the blank of shoe insert to take a final form, and still further that the glued layers of foam bodies are susceptible to detachment eventually, and finally that the shoe insert is vulnerable to distortion caused by the baking process in which the foam bodies made of different foam materials contract unevenly under a high temperature of the baking process. The shortcomings of the shoe insert described above are also shared by the shoe insole or the ornamental article, which is made of the prior art foam bodies described above.